Art of cracking hydrocarbons



May 18' 1937 E. w, lsoM *2,030,820*

rART 0F CRACKING mmRooARBoNsn l 'INVENTOR Edu/am' Mjfam A BY Y l Mns Patented May 18, 1937 PATENT OFFICE ART f or CRACKING HYnRocARBoNs Edward W. Isom, Scarsdale, N. Y., assignor to Sinclair Refining Company, New York, N. Y.,

a corporation of Maine Application October 12, 1929, `Serial No. 399,227y

V4 claims. (ci. 196;-49)

This invention relates to` improvements in the cracking of heavier and higher boiling hydrocarbon oils, such as kerosene, gas oil, fuel oil or residues,:to produce lighter and lower boiling hydrocarbon oils, such as gasoline or gasoline-con taining cracked distillates, therefrom. 'Ihis ap plication is in part a co-ntinuation of my vprior application filed May 21, 1927, Serial No. 193,192. Y This invention provides an improved operation including in combination pressure distillation 'operations producing vresidues and intermediate character `products which the pressure distillation operation itself is not particularly adapted to handle and another cracking operation particularly adapted to handle both such residues and such intermediate character products.

. Where gas oil is cracked for the production of gasoline or a gasoline-containing pressure distillate by pressure distillation, for example, the products of the operation may include a tar or residue and a refractory intermediate fraction such as the bottoms remaining on re-distillation or fractionation of the pressure distillate to separate the gasoline content thereof. This intermediate fraction is usually quite refractory, and in many pressure distillation operations its further treatment in the same operation would impose a burden greater than the benefit derived. likewise, such tar or residue is of a character 'such that its further treatment in many pressure distillation operations involves difficulty due to .excessive formation of pitch or carbon.

In accordance with this invention, such refractory intermediate stock from the pressure distillation operation is forced through a heating conduit into a receptacle from which vapors are taken 01T and subjected in this heating conduit to severe cracking conditions adapted to produce therefrom additional quantities of the desired gasoline product, and such tar or residue is supplied directly to this receptacle heated, entire-ly or largely, by the heat of the hot o-il products discharged into it from the heating conduit. The intermediate character stock is thus subjected to appropriate conditions for its further cracking even though refractory and the tar or residue is thus alsosulojected to further cracking. under conditions avoiding diiculties due to bined operation of the invention, but it is in-V tended and will be understood that this further description and illustration are for the purpose of exemplication and that the invention ris not limited thereto.

The pressure still illustrated comprises a bulk supply drum I, a battery of heating tubes 2 arranged in a heating furnace 3, and circulating connections 4, 5 and 6 including a circulating pump 'I arranged for circulating oil fromthe bulk supply drum upwardly through the' heating tubes and back to the bulk supply drum, the v oil being heated to a cracking temperature in the heating tubes and vapors being taken off from the bulk supply drum vunder superatmos-- pheric pressure. Higher boiling components of the vapors from the bulk supply drum I are condensed in the reflux tower 8 and returned to the circulating charge of Y oil in the pressure still'. This condensation may be eiected or controlled, for example, by regulated introduction of -raW oil to be supplied to the pressure still into the upper end of the reflux tower. Intermediate boiling components ofthe vapors from the reux tower 8 are condensed in the fractionating tower S and conveyed to the supply tank I0 through connection II. This condensation may be effected or controlled, to produce directly a gasoline product of the desired boiling range, for example, by regulated circulation of an indirect cooling medium through a coil in the upper end of the fractionating to-Wer or by regulated introduction of a direct. cooling medium into the upper end of the fractionatng tower or by both of these means. Vapors from the fractionating tower 9, including the gasoline product, escape to a conventional condenser and receiver through connection I3. Tar or residue is discharged from the bulk supply drum I through connection I2. l

Pressure in the pressure still may be maintained and regulated by means of appropriate valves between the reux tower' and thefractionating tower, between, the fractionating tower and the condenser, or beyond the condenser or receiver.

gasoline, for example, the pressure still may be In the cracking of gas oil to produce operated under a pressure in the neighborhood of -300 pounds per square inch.

The vbulk supply drum, the circulating connections, the reiiux tower, the fractionating tower Aand the several hotA connections are with advantage lagged or thermally insulated.

The othercracking still illustrated comprises a still -or drum I5 anda heating conduit I6 ar-V ranged in a heating furnace I'I. A body of oil, or of oil approaching coke, is maintained in the drum I5, usually under superatmospheric pressure, and a stream of oil from the supply tank I is forced through the heating conduit IS into this body of oil, being heated to a high cracking temperature, 1000-1100 F. for example, in the heating conduit. The body of oil in the drum I is thus heated to a cracking temperature, 725-775 F. for example, by heat internally supplied by the hot oil products discharged from the heating conduit I 6. geously externally unheated; it may however be mildly heated externally by means of the furnace I8. Usually the furnace I8 is employed onlyj in initiating operation.

Higher boiling components of the vapors from the drum I5 are condensed in the fractional condenser IS and intermediate boiling components of these vapors are condensed in the fractional condenser 25, These condensations may be ef# fected or controlled, for example, by regulated circulation of raw oil to be supplied tothe drum I5, a crude or a topped crude or a fuel oil for example, through these fractional condensers in indirect heat exchange with the vapors therein. Condensate from condenser I9 may be either conveyed to the pressure still `through connection 2| or `conveyed to supply tank I0. Condensate from condenser is conveyed to supply tank I0. Vapors from the fractional condenser 20 including additional quantities of the gasoline product escape to a conventional condenser and receiver through connection I4. Tar or residue may be discharged from drum I5 through connection 22.

Pressure in the drum I5 may be maintained and regulated by means of appropriate valves between the drum and the fractional condensers, between the fractional condensers, between vthe fractional condensers and the nal condenser or beyond the nal condenser or receiver. In the combined operation of the invention, the drum I5 may be operated undera superatmospheric pressure lower than that prevailing in the pressure still, in the neighborhood of 50-150 pounds per square inch, for example, or under higher pressure. The drum I5, although less advantageously if a maximum production of a gasoline product is desired, may be operated under atmospheric or a slightly higher pressure. The heating conduit I 6 may be operated under a pressure just suicient to effect discharge of the hot oil products therefrom into the drum I5; or the heating conduit I6 may be operated under a higher pressure and this pressure regulated and reduced by means of an appropriate valve between the heating conduit I 6 and the drum I5.

The drum I5, particularly when externally unheated, the fractional condensers and the sev eral hot connections are with advantage lagged or thermally insulated.

The pressure still illustrated may be one of a battery of several; branch connections II', I2' and ZI are provided in the apparatus illustrated for connection to other similar pressure stills of a battery of several.

In carrying out the invention in the apparatus illustrated, the pressure still may be operated, for example, as described in Letters Patent No. 41,598,136, granted to Sinclair Refining Company, August 31, 1926, on the application of Eugene C. Herthel. The reflux tower and the fractionating tower connected to the pressure still may be operated, for example,'as described in applica- The drum I5 is advanta-V ao'sdse tion Serial No. 3,987, filed January 22, 1925, by John E. Bell.

In carrying out the invention in the apparatus illustrated, an intermediate stock from the pressure still, in boiling range between the gasoline product from and the condensate refluxed to the pressure still, is forced through the heating conduit I5 in which it is subjected to severe cracking conditions adapted to produce additional quantities of the gasoline product therefrom, and the tar or residue from the pressure still is supplied tothe drum I5 in which it is subjected to further cracking bythe heat of the hot oil products discharged into this drum from the heating conduit. The drum I5 may be operated to reduce to coke the residue accumulating therein, or to reduce this residue to a heavy flux or pitch, .discharged asA aliquid from the drum I5. Raw

poil, gas oily for example, may be supplied to the pressure still through connection 23. Raw oil, easily cracked raw cil or raw oil including residual components, heavy gas oil or fuel oil or` crude oil or topped crude oil for example, may be supplied to drum I5 through connection 24.

Raw oil, refractory raw oil, light gas oil or kerosene for example, may be supplied to tank I0 through connection 25. The stock supplied to the heating conduit I5 includes in admixture the intermediate stock from the pressure still and the condensate from condenser 20 or from condensers I9 and 2E), and may include additional raw oil supplied through connection 25. The stock supplied to the drum I5 includes the tar or residue from the pressure still` and may include additional raw oil supplied through connection 24.

The improved combined operation of the invention improves the pressure distillation operation included in the combination in several respects. The invention makes it possible to relieve the pressure still of the burden of handling refractory components of intermediate stocks produced in the pressure still without prejudice to stock economy and at the same time makes it possible to. relieve the pressure still of an increased part of the burden of handling pitch components of tar or residue produced in the pressure still without prejudice to operating economy but rather with joint advantage with respect to stock economy and operating economy.

It will be apparent that the invention, in one aspect, provides an improved method of further cracking pressure still tar and particularly of further cracking pressure still tar under superatmospheric pressure. It will also be apparent that the invention, in anotheraspect, provides an improved method of narrowing the range of stocks which the pressure still must handle to that range over which it is most effective.

I claim:

l. In combination with pressure distillation operations for the manufacture of gasoline by cracking heavier and higher boiling hydrocarbonoils, the improvement which comprises taking off from the pressure distillation an intermediate stock higher boiling than the gasoline product and lower boiling than the stock subjected to the pressure distillation and a tar including pitch constituents produced in the pressure distillation, forcing this intermediate stock through a heating conduit and heating it to a. high cracking temperature therein and discharging the hot oil products from this heating conduit into a separate receptacle from which vapors are taken off, and introducing this tar directly into this receptacle and there cracking it further by the heat ofthe hot oil products discharged from the heating conduit.

2. In combination with pressure distillation operations for the manufacture of gasoline by cracking heavier and higher boiling hydrocarbon oils, the improvement which comprises taking off from the pressure distillation an intermediate stock higher boiling than the gasoline product and lower boiling than the stock subjected to the pressure distillation and a tar including pitch constituents produced in the pressure distillation, forcing this intermediate stock through a heating conduit and heating it to a high cracking temperature therein and discharging the hot oil products from this heating conduit into a separate receptacle from which vapors are taken olf, and introducing this tar directly into this receptacle and there cracking it further entirely by the heat of the hot oil products discharged from the heating conduit.

3. In combination with pressure distillation operations for the manufacture of gasoline by cracking heavier and higher boiling hydrocarbon oils, the improvement which comprises taking off from the pressure distillation an intermediate stock higher boiling than the gasoline product and lower boiling than the stock subjected to the pressure distillation and a tar including pitch constituents produced in the pressure distillation,

forcing this intermediate stock through a heating conduit and heating it to a high crackingv temperature therein and discharging the hot oil products from this heating conduit into a separate receptacle from which vapors are taken off, and introducing this'tar directly into this receptacle and there cracking it further under superatmospheric pressure by the heat of the hot oil prodl heating it to a high cracking temperature therein and discharging the hot oil products from this heating conduit into a separate receptacle from which vapors are taken off, and introducing this tar directly into this receptacle and there cracking it further under superatmospheric pressure entirely by the heat of the hot oil products discharged from the heating conduit.

EDWARD W. ISOM. 

